As is well known, building components made of cement must generally meet special requirements for mechanical strength, compressive, tensile and bending stresses and also for nail-pull resistance, compactness, impermeability, adhesiveness to wall surfaces, volumetric stability during setting and hardening, and durability, i.e. of resistance for a long time to environmental conditions which sometimes are particularly severe.
Recently, moreover, in the place of the traditional light mortars for plasters, cementitious materials are used, which contain polystyrene beads previously coated with resins or glues and a filler to make then rough and which provide lighter products for application to the bearing surfaces of buildings, such products being endowed with good characteristics of thermal and acoustic insulation and water-repellency. These cementitious products are effectively used mainly as additional components, with the purpose of increasing the thermal and acoustic insulation and the water-repellency characteristics of slabs or bearing panels or masonry constructions, mainly in countries with extremely sharp temperature fluctuations, and therefore with frequent freeze-thaw cycles.
For example, in U.S. Pat. No. 3,967,005, issued Jun. 29, 1976 to Mario Cattaneo, there is disclosed a method of and apparatus for enveloping pellets of foamed polystyrene in which the pellets are mixed in a mixing unit with water and synthetic resin and, subsequently, with an inert filler, and then passed to a heating zone for drying and/or polymerization.
Normally, in prefabricated buildings, particularly in northen countries, the walls of those buildings are composed of various layers of materials, in a well known way, at least one of which comprises a cementitious product containing coated polystyrene beads for the purpose of substantially improving the insulating characteristics of the walls, as can be shown by experimental and practical tests.
Such cementitious products, however, must necessarily be applied only as additional materials combined with the bearing elements of the prefabricated buildings, with a consequential increase of the manufacturer's time costs.